Nair and Adams, Journal of the American Chemical Society, Volume 33, pages 3518-3521 (1961) describe the preparation of certain tricyclic morpholinobenzimidazole compounds optionally having a chloro, methyl or nitro substituent at the 5-position. Fielden, et al., Journal of the Chemical Society, No. 7, pages 696-701 (1973) report the preparation of tricyclic morpholinobenzimidazole N-oxide and its 5-nitro derivative by cyclization of the corresponding ortho-nitrophenylmorpholine compound.